Penn State Victim Reveals Himself & Speaks Out For 1st Time! (Video)

Aaron Fisher, 18, has written a book, Silent No More: Victim 1's Fight for Justice Against Jerry Sandusky, with his psychologist, Mike Gillum, and his mother, Dawn Daniels, to be published on Oct. 23 by Random House.

"Saying sexual abuse has happened was hard,"

says Fisher in an exclusive interview with PEOPLE, on newsstands next week.

"But I wanted to help people see that it is better to come forward and tell somebody than to be silent."

It took Fisher – who says he was abused by Sandusky from the ages of 12 to 15 – three years before he found the courage to tell his mother and officials at his high school. By speaking out, he helped launch the investigation, which eventually led Sandusky to be convicted on 45 counts of sexual abuse. On Oct. 9, Sandusky was sentenced to 30-60 years in prison.